Scientists and engineers often employ seismic surveys for exploration, geophysical research, and engineering projects. Seismic surveys can provide information about underground structures, including formation boundaries, rock types, and the presence or absence of fluid reservoirs. Such information greatly aids searches for water, geothermal reservoirs, and mineral deposits such as hydrocarbons and ores. Oil companies in particular often invest in extensive seismic surveys to select sites for exploratory oil wells.
Conventional seismic surveys employ artificial seismic energy sources such as shot charges, air guns, or vibratory sources to generate seismic waves. The sources, when fired, create a seismic “event”, i.e., a pulse of seismic energy that propagates as seismic waves from the source down into the earth. Faults and boundaries between different formations create differences in acoustic impedance that cause partial reflections of the seismic waves. A seismic sensor array detects and records these reflections for later analysis. Sophisticated processing techniques are then applied to the recorded signals to extract an image or other representation of the subsurface structure.
Unfortunately, seismic analysts often find that certain subsurface features are poorly imaged or inadequately distinguishable. In such circumstances, the only solutions are to pursue a more sophisticated processing technique or push for additional data acquisition in the previously-surveyed area. Each of these solutions can be prohibitively expensive in terms of time and money.